The SENSEI® RX180iN condensing tankless water heater from Rinnai is only the size of a small suitcase, uses either Natural Gas or Propane, and can be installed indoors or outdoors using the Versa-Vent™ accessory. Rinnai SENSEI® RX Series tankless water heaters last up to twice as long as tanks and have twice the warranty length. Plus, they save energy by heating water only when it is needed.